1. Field of the Invention
This invention relates generally to injection molding. In particular, this invention relates to so-called hot runner constructions comprising manifold and nozzle assemblies for conducting flow of melt from an injection unit to one or more mold cavities.
2. Description of Related Art
It is known to provide injection molding equipment comprising constructions of a manifold and associated nozzle assemblies where nozzle assemblies are connected to a material distributing manifold member by engagement of threads of a body of a nozzle with threads of the manifold member. Alternative arrangements provide for connection of a nozzle assembly to a manifold member by a threaded member (nut) engaging threads of the manifold member and engaging a retention element of a nozzle body so as to clamp the nozzle to the manifold member.
In the known constructions of manifold and nozzle assemblies, melt passages of the nozzle assemblies are in direct communication with melt passages of the manifold. A manifold member is required that is peculiar for each size of nozzle melt passage to be used. That is, because of the direct communication between melt passages of nozzle assemblies and the manifold melt passages, it is not possible to substitute nozzle assemblies having nozzle passages of different cross-sectional sizes one for another for attachment to a particular manifold member. Because it is desirable to select nozzles according to material being processed and characteristics of mold cavities, it is desirable to substitute nozzles one for another in constructions of manifold members and nozzle assemblies.
Appropriate alignment of nozzle assemblies with material distributing manifold members is required to enable unimpeded flow of material from a manifold passage into a nozzle passage and to prevent leakage at the interface between a nozzle assembly melt passage and a manifold member melt passage. It is known to achieve the desired alignment by direct contact of an alignment surface of the manifold member with a surface of the nozzle body or retention device.
In general, known methods of threaded engagement for retention of nozzles with manifold members are not effective to accommodate differences between cross sectional size of a manifold passage outlet and a nozzle passage inlet. As a consequence of this deficiency of known constructions, it is necessary to provide manifold members made to accommodate particular nozzles. Therefore, nozzles having differing nozzle passage cross sectional sizes can not be substituted one for another in such manifold and nozzle assembly constructions. Hence, there remains a need for improved constructions for retention of nozzles with manifold members to accommodate substitution of nozzle assemblies of differing melt passage cross-sectional size while achieving desired alignment of melt passages of nozzle assemblies with melt passages of manifold members so as to facilitate flow of material from the manifold passage into the nozzle passage and eliminate or reduce to an acceptable level leakage of material as it is conveyed from a manifold passage into a nozzle passage.